如何创建类< T>的开放通用类型的列表? [英] How to create List of open generic type of class<T>?

问题描述

我正在处理其他人的代码，我需要添加一些内容 我上课

i am working on someone else code i need to add few things i have a class

public abstract class Data<T>
{

}

public class StringData : Data<string>
{
}

public class DecimalData : Data<decimal>
{
}

在我的程序中，我想维护不同类型数据的列表

in my program i want to maintain list of different type of data

List<Data> dataCollection=new List<Data>();

dataCollection.Add(new DecimalData());
dataCollection.Add(new stringData());


List<Data> dataCollection=new List<Data>();

在上一行的

我遇到了编译器错误 使用通用类型数据"需要1个类型参数

at above line i am getting compiler error Using the generic type 'Data' requires 1 type arguments

任何人都可以指导我做错了吗

Can any one guide what i am doing wrong;

推荐答案

C#中尚无Diamond运算符，因此您不能对基于封闭构造类型的开放泛型类型使用真正的多态性.

There is no diamond operator in C# yet, so you can't use true polymorphism on open generic type underlying to closed constructed types.

泛型-打开和关闭的构造类型

通用类(C#编程指南)

所以您不能创建这样的列表:

So you can't create a list like this:

List<Data<>> list = new List<Data<>>();

您不能在这样的列表上使用多态性...而且这里缺乏通用性.

You can't use polymorphism on such list... and it is a lack in genericity here.

例如，在C#中，您无法创建List<Washer<>>实例来具有一些Washer<Cat>和一些Washer<Dog>来对它们进行操作Wash() ...

For example, in C# you can't create a List<Washer<>> instance to have some Washer<Cat> and some Washer<Dog> to operate Wash() on them...

您所能做的就是使用对象列表或丑陋的非通用接口模式:

All you can do is using a list of objects or an ugly non generic interface pattern:

public interface IData
{
  void SomeMethod();
}

public abstract class Data<T> : IData
{
  public void SomeMethod()
  {
  }
}

List<IData> list = new List<IData>();

foreach (var item in list)
  item.SomeMethod();

您还可以使用非通用抽象类代替接口:

You can also use a non generic abstract class instead of an interface:

public abstract class DataBase
{
  public abstract void SomeMethod();
}

public abstract class Data<T> : DataBase
{
  public override void SomeMethod()
  {
  }
}

List<DataBase> list = new List<DataBase>();

foreach (var item in list)
  item.SomeMethod();

但是您失去了一些通用性设计和强大的功能...

But you lost some genericity design and strong-typing...

您还可以提供任何非通用行为，例如您需要对其进行操作的属性和方法.

And you may provide any non-generic behavior such as properties and methods you need to operate on.

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